timekeeping: Simplify code in timekeeping_advance()

timekeeping: Simplify code in timekeeping_advance()

timekeeping_advance() takes the timekeeper_lock and releases it before
returning. When an early return is required, goto statements are used to
make sure the lock is realeased properly. When the code was written the
locking guard() was not yet available.

Use the guard() to simplify the code and while at it cleanup ordering of
function variables. No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-5-554456a44a15@linutronix.de